kein Blatt vor den Mund nehmen

Etymology
lit. 'not to take a leaf/sheet in front of one’s mouth'. Compare the same in 🇨🇬. Further origin uncertain. Sometimes claimed to derive from a custom among stage actors, who apparently used tree leaves or sheets of paper as a kind of mask. Also said to be from the use of a sheet of paper to muffle one’s voice when speaking privately in company. Perhaps eventually based on the metaphorical as a means of concealing the rude or indecorous.

Verb

 * 1)  to be outspoken; not to mince words; to call a spade a spade